1. Field of the Invention
This invention relates generally to magnetic storage systems, and more particularly, to air bearing sliders for use in magnetic storage systems.
2. Description of Related Art
A magnetic storage system typically includes one or more magnetic disks with at least one data recording surface having a plurality of concentric tracks for storing data. A spindle motor and spindle motor controller rotate the disk(s) at a selected RPM such that at least one read/write transducer or "head" per recording surface can read data from or write data to each recording surface. The data read or written from each recording surface is processed by a read/write channel. The transducer is supported by an air bearing slider which has a top surface attached to an actuator assembly via a suspension, and a bottom surface having an air bearing design of a desired configuration to provide favorable flying height characteristics. During the operation of the magnetic storage device, the air bearing slider is positioned in close proximity above the desired data track by an actuator assembly. The movement of the actuator assembly above the disk surface is controlled by a servo system.
Conventional magnetic storage systems may operate in a contact start/stop mode where the slider and transducer are only in contact with the recording surface when the spindle motor is powered down. As the disk begins to rotate, an air flow is generated which enters the leading edge of the slider and flows in the direction of the trailing edge of the slider. The air flow generates a positive pressure on the air bearing surface of the slider to lift the slider above the recording surface. As the spindle motor reaches the operating RPM, the slider is maintained at a nominal flying height over the recording surface by a cushion of air. Then, as the spindle motor spins down, the flying height of the slider drops until the slider is once again in contact with the disk.
FIGS. 1A-1B illustrate a prior art slider design as disclosed in U.S. Pat. No. 5,404,256, issued Apr. 4, 1995 to James W. White, entitled "TRANSVERSE AND NEGATIVE PRESSURE CONTOUR GAS BEARING SLIDER." The air bearing design of slider 100 is suitable for a magnetic storage system that operates in a contact start/stop mode. Slider 100 is designed to provide uniform and controllable flying height through a range of skew angles.
According to FIGS. 1A-1B, pads 122 each include a generally U-shaped transverse pressure contour (TPC) section 128 surrounding an air bearing surface 134. TPC sections 128 have a substantially planar surface for creating a gas bearing effect. A negative pressure pad 126 is defined by a substantially planar surface that includes a recess 140 open at a trailing end 125 of slider 100. The negative pressure pad 126 may also include one or more air bearing surfaces 142. An ambient pressure reservoir 130 defines a cavity 144 having a depth and configuration sufficient to maintain substantial ambient pressure in cavity 144 during movement of the disk. Ambient pressure reservoir 130 also includes a non-tapered inlet along a leading edge 123.
As shown in FIGS. 1A-1B, slider 100 has sharp corners and edges and air bearing surfaces 134 and 142 also have sharp corners. One drawback of having an air bearing surface with sharp edges and corners is that during the contact start or stop, the sharp edges of the air bearing surface may cause deformations on the surface of the disk as the slider is being lifted off or placed onto the disk surface. One approach to reduce the amount of damage resulting from the slider-to-disk contact is to round the edges of the air bearing rails as shown in U.S. Pat. No. 4,928,195 or to provide air bearing rails with beveled edges as shown in U.S. Pat. No. 5,301,077. By rounding or beveling the air bearing rail edges, unwanted wear of the disk surface is reduced. However, when the edges of the air bearing surface are rounded, the slider flying height may be adversely affected.
In many conventional magnetic storage systems that operate in a contact start/stop mode, the slider drags on the disk surface until sufficient air-bearing is generated to lift the slider off the disk surface. This start-stop process leads to two problems at the head/disk interface: (1) wear of the disk surface (also referred to as wear durability) and (2) adhesion of the slider to the disk surface during start-up (also referred to as stiction). One approach to circumvent the undesirable issues associated with wear durability and stiction is to use load/unload technology.
Typically, load/unload technology includes a ramp for the slider/suspension assembly at the outer diameter of the disk where the slider is "parked" securely while the spindle motor is powered down. During normal operation, the disk speed is allowed to reach a selected RPM (which may be below the normal operating RPM) before the head is "loaded" from the ramp onto the disk. As the slider approaches the disk surface, an air cushion is generated by the disk's rotation. The slider can also be "unloaded" from the disk's surface onto the ramp. In this manner, the slider is positioned over the disk without substantial contact with the disk surface. By reducing the contact between the slider and the disk surface, the interface life can be substantially increased. Because the slider and transducer are generally not in contact with the disk surface during start-up, stiction is not a problem. As such, a smooth (or non-textured) disk surface may be used with load/unload designs to decrease the head-to-disk spacing in order to increase the areal density of the disk.
One drawback associated with load/unload designs is that when the slider is being "loaded" onto the disk surface, the corner of the slider may contact the disk surface before an air-bearing can be developed. This contact results in both slider wear and damage to the disk surface.
Furthermore, when the slider is being "unloaded" from the cushion of air above the disk surface onto the ramp, sliders having negative pressure air bearing designs generally resist being pulled away from the disk surface. The negative pressure region of the slider has a tendency to pull the slider toward the disk surface by a suction force as the suspension attempts to lift the slider. Eventually, the slider/suspension assembly overcomes this suction force in order to lift the slider onto the ramp. As soon as the suction force is released, the stored energy (often referred to as spring energy) within the suspension assembly causes the suspension to snap the slider away from the disk surface. This snapping motion causes the slider to oscillate or vibrate. Typically, at this point the slider is just starting to ride up the ramp such that the corners, and possibly the edges, of the vibrating slider may contact the disk surface with sufficient force causing damage to the disk surface.